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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 374 journals)
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Journal of the Indian Institute of Science
Journal Prestige (SJR): 0.212
Citation Impact (citeScore): 1
Number of Followers: 3  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0970-4140 - ISSN (Online) 0019-4964
Published by Springer-Verlag Homepage  [2469 journals]
  • The Development of Bayesian Statistics

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      Abstract: Abstract The incorporation of Bayesian inference into practical statistics has seen many changes over the past century, including hierarchical and nonparametric models, general computing tools that have allowed the routine use of nonconjugate distributions, and the incorporation of model checking and validation in an iterative process of data analysis. We discuss these and other technical advances along with parallel developments in philosophy, moving beyond traditional subjectivist and objectivist frameworks to ideas based on prediction and falsification. Bayesian statistics is a flexible and powerful approach to applied statistics and an imperfect but valuable way of understanding statistics more generally.
      PubDate: 2022-05-21
       
  • IntroSurvey of Representation Theory

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      Abstract: Abstract There could be thousands of Introductions/Surveys of representation theory, given that it is an enormous field. This is just one of them, quite personal and informal. It has an increasing level of difficulty; the first part is intended for final year undergrads. We explain some basics of representation theory, notably Schur–Weyl duality and representations of the symmetric group. We then do the quantum version, introduce Kazhdan–Lusztig theory, quantum groups and their categorical versions. We then proceed to a survey of some recent advances in modular representation theory. We finish with 20 open problems and a song of despair.
      PubDate: 2022-05-17
       
  • Non-conventional Small-Scale Mechanical Testing of Materials

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      Abstract: Abstract Development of non-conventional mechanical testing techniques was primarily driven by the requirement to measure mechanical properties at smaller length scales with increasing miniaturization of devices, as well as the need for microstructure design from bottom up. This review covers the techniques involved in determining the small-scale deformation and fracture response of materials under different stress states. This is an attempt to provide a summary of choices and test protocols to potential users based on the property of interest to them. It begins with the basics of test instrumentation and sample preparation, followed by a short introduction to modeling tools that accompany testing, and later gets into the details of individual tests and their advantages and limitations. Selected applications from recent published works are presented to provide a flavor of material systems whose behaviour differs significantly from the macro-scale due to their size and/or architecture. At the end fallacies in data interpretation and a roadmap to standardization followed by ideas and future scope for non-conventional small-scale testing are given.
      PubDate: 2022-05-13
       
  • Guest Editorial: Materials for a Sustainable Future

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      PubDate: 2022-05-10
       
  • Clinician Scientists in the Indian Context

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      Abstract: Abstract Advances in healthcare are fueled by discovery and innovation in science and technology. However, such discovery and innovation cannot occur without vital inputs from a clinician. Here, we make a case for the training of clinicians as scientists and engineers to help integrate over disciplines and accelerate translational research in India. We identify and suggest possible solutions to the challenges of creating an Indian clinician-scientist. We further take stock of programs across the globe, initiatives in India, including at our institute, and highlight possible paths that could be taken to train such individuals. With an adequate investment of effort and time, we believe that the clinician-scientist will have the ability to transform healthcare in India.
      PubDate: 2022-05-04
       
  • Editor’s Desk

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      PubDate: 2022-04-28
       
  • Likelihood Ratio Tests for Elaborate Covariance Structures and for MANOVA
           Models with Elaborate Covariance Structures—A Review

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      Abstract: Abstract In this paper a review is made from the primordia of the history of likelihood ratio tests for covariance structures and equality of mean vectors through the development of likelihood ratio tests that refer to elaborate covariance structures. Relations are established among several covariance structures, taking more elaborate ones as umbrella structures and examining then their particular cases of interest. References are made to bibliography where the corresponding likelihood ratio tests are developed and the distributions of the corresponding statistics addressed. Most of the likelihood ratio test statistics for one-way manova models where the covariance matrices have elaborate structures were developed quite recently. Also for these likelihood ratio tests a similar approach is taken. Although we start with the common test that uses unstructured covariance matrices, then we go on to consider tests with more elaborate covariance structures, and subsequently we specify them to their particular cases of interest. Some special attention is also given to the so-called Wilks \(\Lambda\) statistics.
      PubDate: 2022-04-17
       
  • Review: Fatigue of Fiber-Reinforced Composites, Damage and Failure

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      Abstract: Abstract A concise review of fatigue of fiber-reinforced composites, covering fatigue life and damage development and how the properties of constituents, orientations and other parameters affect fatigue life, is presented. The subject broadly covers polymer, metal, and ceramic matrix composites, by including specific examples of fatigue data from literature. Studies of composite fatigue have mostly evolved over the last 60 years, largely driven by aerospace applications of composites. The field is very vast in terms of accumulated technical literature and fatigue data. Therefore, only some iconic examples, each with good experimental data, have been considered in this review to illustrate the behavior and the trends as clearly as possible. First, the general nature of tensile deformation of fiber composites under various combinations of fiber and matrix failure strains are reviewed to provide a background with which the more complicated fatigue behavior can be easily understood. Second, examples of S–N fatigue data of glass (GFRP) and carbon (CFRP) fiber-reinforced plastics are provided, illustrating the effects of reinforcement, constituent properties, temperature, and orientation effects on fatigue failure. These analyses are also modeled by S–N curve calculations using exponential S–N fatigue constitutive equations proposed by author. These calculations helped to easily rationalize the trends in S–N data, as influenced by strength and failure strains of fiber and matrix. Next, stiffness degradation behavior in fiber composites are reviewed, with specific examples including CFRP (polymer matrix) and SiC/SiC (ceramic matrix) composites. The nature of stiffness degradation is also modeled using a semi-empirical equation that relates the fractional remaining stiffness to fractional remaining fatigue life in the composite. Finally, a few examples of fatigue behavior of laminated composites that are typically used in real-world applications are reviewed.
      PubDate: 2022-03-25
       
  • Bayesian Modeling of Discrete-Time Point-Referenced Spatio-Temporal Data

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      Abstract: Abstract Discrete-time point-referenced spatio-temporal data are obtained by collecting observations at arbitrary but fixed spatial locations \(\varvec{s}_{1},\varvec{s}_{2},\ldots ,\varvec{s}_{n}\) at regular intervals of time \(t := 1,2,\ldots ,T\) . They are encountered routinely in meteorological and environmental studies. Gaussian linear dynamic spatio-temporal models (LDSTMs) are the most widely used models for fitting and prediction with them. While Gaussian LDSTMs demonstrate good predictive performance at a wide range of scenarios, discrete-time point-referenced spatio-temporal data, often being the end product of complex interactions among environmental processes, are better modeled by nonlinear dynamic spatio-temporal models (NLDSTMs). Several such nonlinear models have been proposed in the context of precipitation, deposition, and sea-surface temperature modeling. Some of the above-mentioned models, although are fitted classically, dynamic spatio-temporal models with their complex dependence structure, are more naturally accommodated within the fully Bayesian framework. In this article, we review many such linear and nonlinear Bayesian models for discrete-time point-referenced spatio-temporal data. As we go along, we also review some nonparametric spatio-temporal models as well as some recently proposed Bayesian models for massive spatio-temporal data.
      PubDate: 2022-03-25
       
  • Mutations and the Distribution of Lifetime Reproductive Success

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      Abstract: Abstract Evolution proceeds in large part by the establishment of mutations in the genome of organisms, but even an advantageous mutation may be lost by chance. The probability of such loss is the extinction probability of an individual with a random lifetime reproductive success (LRS). We show here that the traditional approximation of extinction probability in terms of the mean and variance of LRS does not always apply, because the LRS has a skewed, often multimodal, distribution. To exemplify distinct life history patters, we use the Hadza and Pacific Chinook salmon. The traditional approximation overestimates the exact extinction probability from complete LRS distribution. An accurate analysis of the distribution of LRS strengthens our ability to successfully analyze evolution.
      PubDate: 2022-03-25
       
  • Strength–Ductility Synergy in High Entropy Alloys by Tuning the
           Thermo-Mechanical Process Parameters: A Comprehensive Review

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      Abstract: Abstract The strength–ductility trade-off is an eminent factor in deciding the mechanical performance of a material with regard to specific applications. The strength–ductility synergy is generally inadequate in as-synthesized high entropy alloys (HEAs); however, it can be tailored owing to its tunable microstructure and phase stability. Thermo-mechanical processing (TMP) allows the microstructure to be tailored to achieve desired strength–ductility combination. The additional attribute is evolution of texture, which also significantly influences the mechanical properties. This review presents a critical insight into the role of TMP to achieve superior strength–ductility symbiosis at room temperature in single-phase (FCC, BCC) and multiphase HEA. The role of overall processing strategy of HEAs encompassing rolling and subsequent annealing in relation to the evolution of microstructure and texture in have been discussed. Recently practiced severe plastic deformation processes have also shown promise in improving the strength–ductility combination. The relevance of these processes in the processing of HEAs has also been analysed. At the end, futuristic approaches have been elaborated to enable efficient as well as hassle-free process towards achieving the proficiency of strength–ductility in HEAs.
      PubDate: 2022-03-24
       
  • Phase-field Modeling of Phase Transformations in Multicomponent Alloys: A
           Review

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      Abstract: Abstract Almost all alloys of engineering importance are multicomponent in character. Multicomponent alloys are subject to complex interplay of thermodynamic and kinetic parameters and display a rich variety of microstructural features which are not seen in binary alloys. Achieving microstructural control of multicomponent alloys is central to their efficacy in specific applications. Unraveling the chemistry-thermomechanical processing-microstructure relationships in multicomponent alloys only through experiments have been proven to be a resource intensive approach. Quantitative simulations of microstructural evolution in multicomponent alloys using the technique of phase-field modeling can significantly offset the experimental burden and provide an energy efficient and sustainable framework for alloy design. In this review, we focus on those phase-field models which can consider the evolution of multiple phases simultaneously in a multicomponent system and attempt to understand the history of their emergence as tools of predictive value. We briefly review the studies conducted with such multiphase, multicomponent phase-field models and conclude with a commentary on the future role of phase-field modeling towards the sustainable development of novel multicomponent alloys.
      PubDate: 2022-03-20
       
  • Oxidation Behaviour of Ni-Base Superalloys in Supercritical Water: A
           Review

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      Abstract: Abstract In the quest for creating a sustainable future, coal-fired boilers and nuclear reactors are increasingly moving towards higher steam temperatures and pressures that can help in reducing emissions and increase operational efficiencies. This trend has now transitioned to adopting Advanced Ultra-Supercritical (AUSC) water technology that involves steam temperatures and pressures as high as 760 ℃ and 32 MPa. This transition poses serious material challenges, and one such is the demanding steam oxidation resistance expected of the candidate Ni-base alloys. Steam oxidation is a severe problem that can cause significant downtime in power generation. Several studies have focused on testing the steam oxidation resistance of candidate Ni-base alloys in supercritical water environments under varying test conditions. They differ from each other in terms of various operational parameters, including the time, temperature, pressure, alloy surface condition, dissolved oxygen (DO) content, steam flow/stagnancy conditions, and presence of additional oxidants like acids, salt, etc. The presence of so many such variables and the complex interplay between them makes it challenging to compare the oxidation performance of various Ni-base alloys and understand the effect of each operational parameter towards oxidation. In addition, widely differing opinions are being held about the role of several operating parameters in causing steam oxidation. This review work is an attempt to consolidate all such relevant works, critically analyze the results reported, generalize the trends observed, identify the variations among reported works and throw light on the shortcomings.
      PubDate: 2022-03-20
       
  • Packaging Materials in High-Performance Computing Applications

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      Abstract: Abstract What drove electronics to what it is today is transistor scaling. But the emerging trend for computing, along with smartphones, IoTs and wearables and all other small systems as well as a new era in automotive electronics, requires a new electronics system. A new system technology frontier, enabled by scaling of system components and system interconnections, is emerging to address this need. This requires a next-generation set of materials to realize system functions such as digital, optical, thermal, RF, mm wave, power, etc. This paper reviews the key system component and packaging needs, advances and emerging materials for computing applications. Glass-based device and systems packaging for such systems are ideal for scaling because of its many advantages such as dimensional stability, low loss, large-area panel-scale processability, surface smoothness, matched CTE with silicon, chemical inertness, etc. High-performance computing is also driving the need for unprecedented material advances in low-permittivity and low-loss thin-film package substrate dielectrics with high temperature, high-power handling and ultra-high reliability. For power supply, a major leap in energy storage densities is achieved with ultrahigh density capacitors from nanoscale surfaces and nanomagnetic inductors. Such nanostructures also minimize power consumption by enhancing the power conversion efficiency. Nanocopper-based interconnections, without solders, and yet assembled at low temperature, below 200 °C drive the next wave of assembly manufacturing and reliability innovation.
      PubDate: 2022-03-20
       
  • Empirical Bayes and Selective Inference

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      Abstract: Abstract We review the empirical Bayes approach to large-scale inference. In the context of the problem of inference for a high-dimensional normal mean, empirical Bayes methods are advocated as they exhibit risk-reducing shrinkage, while establishing appropriate control of frequentist properties of the inference. We elucidate these frequentist properties and evaluate the protection that empirical Bayes provides against selection bias.
      PubDate: 2022-03-07
      DOI: 10.1007/s41745-022-00286-0
       
  • Quasicrystals: A New Class of Structurally Complex Intermetallics

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      Abstract: Abstract Quasicrystals are considered as a new class of intermetallics with the long-range quasiperiodic ordering, and have attracted research interest over the last 3 decades due to their interesting structural complexities, unique physical/mechanical properties, and potentials for applications. Quasicrystals exhibit ultimate complexity with a lack of periodicity in the 3-dimensional space, but give rise to sharp diffraction patterns with rotational symmetry forbidden for periodic crystals. The crystal structure of quasicrystalline intermetallics can be understood in terms of appropriate decoration of 3-dimensional Penrose quasilattice using higher dimensional crystallography. Here, we have reviewed research outcomes in the area of quasicrystals, with an emphasis on the synthesis, structure, stability, as well as  properties, and potential applications related to mostly icosahedral quasicrystals and other relevant complex intermetallics.
      PubDate: 2022-03-07
      DOI: 10.1007/s41745-022-00293-1
       
  • Accelerated Electro-Reduction of TiO2 to Metallic Ti in a CaCl2 Bath Using
           an Inert Intermetallic Anode

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      Abstract: Abstract In the FFC-Cambridge process, the cathodic dissociation of oxide and CO/CO2 production on carbon anode is the basis for metal production in a CaCl2 bath. Using an inert intermetallic anode, the CO2 evolution can be eliminated altogether with acceleration in the electro-reduction kinetics. In the presence of a carbon anode, the cathodic dissociation of TiO2 suffers from slow reduction kinetics of TiO2 to Ti metal, which can be enhanced significantly by the incorporation of alkali species in the TiO2 pellet at the cathode and in the CaCl2 bath in the presence of an intermetallic inert anode. With inert anode and incorporation of K+-ion in the TiO2 matrix and in the salt bath, nearly full metallization with greater than 99% of Ti metal containing 1500 ppm of oxygen was possible to achieve in less than 16 h of electro-reduction. The microstructural and chemical analysis of the metallic phase and its morphology revealed the presence of a layer of titanium metal that forms in the fast reduction reaction step in less than 5 h, after which the reaction rate slows down significantly before terminating in 16 h. The investigation showed that two different types of microstructures of metallic titanium were evident—a thin sheet-like material on the outer periphery of the reduced pellet and the dendritic core which was found to be under the peripheral sheet of the metallic layer. The mechanism of morphological and microstructural changes in the reduced form of titanium metal is explained.
      PubDate: 2022-03-07
      DOI: 10.1007/s41745-022-00296-y
       
  • Materials for Gas Turbine Engines: Present Status, Future Trends and
           Indigenous Efforts

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      Abstract: Abstract Gas turbine engines ingest air from the ambient atmosphere and produce power using the energy of the combustion products of the highly compressed air for generation of electricity, pumping natural gases, powering ships and propelling aircrafts. The device consists of a large number of components manufactured using atleast twenty five different alloy grades to meet the performance requirements under highly demanding operating conditions. The material selection during mechanical design of the system demands consideration of various complex damage mechanisms experienced in service. This necessitated development and production of high quality material systems. Remarkable improvement in the engine performance over the years was possible due to a continuous evolution in materials and associated technologies. The demand in the availability of the suitable materials to achieve the targeted performance of the engines yielded improved alloy systems (steel, titanium alloys and superalloys), melting practices (air melt to vacuum induction melting), wrought forming and casting technologies. Composites, intermetallic and several new material systems are also being explored and some of them are successfully inducted into the application. This paper captures the material requirements in a gas turbine engine along with global and national efforts in establishing the technologies for materials in the system.
      PubDate: 2022-02-28
      DOI: 10.1007/s41745-022-00295-z
       
  • Development of Advanced Nuclear Structural Materials for Sustainable
           Energy Development

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      Abstract: Abstract Structural materials used in nuclear reactors face many challenges due to elevated temperature operation, high neutron flux induced transmutations and radiation damage. In the present article, we review the core structural materials used in thermal as well as fast reactors. Due to emphasis on neutron economy and relatively low temperature operation, Zirconium-based alloys are used in thermal reactors and their evolution and materials challenges are discussed. In the case of fast reactors, due to intense fast neutron flux and high temperatures, austenitic stainless steels and its variants are used. Advanced structural materials with better radiation performance and for enhanced burn-up applications are also discussed.
      PubDate: 2022-02-28
      DOI: 10.1007/s41745-022-00287-z
       
  • Fractional Processes and Their Statistical Inference: An Overview

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      Abstract: Abstract We give an overview of properties of fractional processes such as fractional Brownian motion, mixed fractional Brownian motion, sub-fractional Brownian motion, fractional Lévy process , fractional Poisson process and present a short review of problems of statistical inference for processes driven by fractional processes.
      PubDate: 2022-02-24
      DOI: 10.1007/s41745-021-00271-z
       
 
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